Communications system for remote control systems

ABSTRACT

A communications system for transmitting and receiving remote control messages in an electronic remote control system. The present communications system uses a remote control message protocol which is particularly suitable for transmitting RF remote control messages with IR remote control messages in a time multiplexed fashion, wherein the RF remote control messages are transmitted during the pause intervals between IR remote control message transmission intervals. The present remote control message protocol includes a start sequence, comprising a MARK pulse and a SPACE of about equal duration, followed by a plurality of data fields. Each data field ends with an End of Field marker and the remote control message ends with an End of Message marker. The plurality of data fields comprises an addressing data field for specifying the destination device, a security code data field for allowing a specific remote control transmitter to control a specific destination device, a status field for specifying various status codes associated with the remote control message, a keycode field for carrying the remote control message payload, and a checksum field for verifying the transmission integrity of the remote control message. A remote control message based on the present message protocol may be expanded to include additional data fields and to expand pre-existing data fields.

This application claims benefit of provisional application Nos.60/036,794, filed Jan. 31, 1997 and 60/038,893, filed Feb. 20, 1997.

BACKGROUND OF THE INVENTION

The present invention relates to a communications system, and moreparticularly to a communications system for transmitting and receivingremote control messages to control electronic devices.

A variety of remote control systems that transmit and receive remotecontrol messages to control various electronic devices are known. Suchsystems typically include a remote control device which comprises aninput device, such as a keypad, for allowing user input, coupled to acontroller which is in turn coupled to a signal transmitter. In responseto a user input, the controller generates an appropriate remote controlmessage using look up tables, and the like, from memory and causes asignal transmitter to transmit the remote control message. The signaltransmitter may be designed to transmit the remote control message in anumber of different forms, including, but not limited to, an IR signaland a RF signal.

One commonly used method of sending a remote control message is totransmit the message in IR signal form. Remote control devices thattransmit IR signals are well known and commonly used with householdelectronic devices. The message format of the IR signal is determined bythe manufacturer for each model and many such IR message formats areknown and used. Each format specifies a set of message characteristics,which include, but are not limited to message duration, transmission andpause intervals and types of data carried in the remote control message.

However, there are several disadvantages associated with using IRsignals to control an electronic device. First, the IR signal isdirectional and as such requires the user to point the remote controldevice toward the destination device for proper transmissionperformance. Also, the IR signal may have a relatively short range andbe easily blocked by objects such as walls, floors, ceiling and thelike, so a remote control device must generally be used in the same roomin which the destination device is located.

Also, many existing IR signal message formats do not have sufficientdata carrying capacity to transmit all of the different types of remotecontrol data required for controlling many modern electronic devices.For example, in addition to the conventional remote control messagesassociated with household electronic devices, such as ON, OFF, ChannelUp, Channel Down, etc., many modern electronic devices, such assatellite receivers, may require the remote control device to send otherforms of data, such as ASCII character data. Many existing IR signalmessage formats are not designed to handle such additional forms of dataand/or simply do not include enough capacity to carry the data.

Another method of sending a remote control message is to transmit themessage in RF signal form. RF signals are generally non-directional andhave greater range than IR signals. RF signals may also be transmittedthrough objects such as walls, and the like, so that the user can usethe remote control device to control a device in a separate room. Thisextended range and ability to transmit messages through objects isbeneficial in situations where a central device, such as a set top boxor a satellite receiver, provides input to a plurality of deviceslocated throughout different rooms in a building. Also, RF signalmessage formats generally have wider bandwidths, and thus have greaterdata carrying capacity, than existing IR signal formats.

As such, it is desirable to be able to use RF signals to control modernelectronic devices. However, devices and methods using IR signals remainpopular and are widely used. In order to maintain backwardcompatibility, i.e., allow a remote control device to control existingdevices which utilize IR signals, a remote control device should also becapable of transmitting IR signals. Therefore, it is desirable to havean apparatus and a method for easily and efficiently transmitting somecombination of IR and RF signals to take advantage of the features ofthe two signal transmission forms.

However, existing IR signal message formats, or protocols, are nottotally suitable for transmitting remote control messages in RF form.Since, the RF signals have longer range and transmit through objectsbetter than IR signals, a RF signal message format must include a methodof preventing interference from neighboring RF signal transmitters.Also, existing IR signal message formats do not allow a remote controldevice to send different types of data, such as ASCII data, in additionto the standard IR signal commands. Further, existing IR signal messageformats do not take full advantage of the increased bandwidth andexpandability associated with RF signals. Limited use of the availablebandwidth and limited expandability reduces the ability to efficientlytransmit and receive additional data, as well as more complex data,thereby limiting the ability to add new types of remote control devicesto an existing system and incorporate new features to existing remotecontrol devices.

SUMMARY OF THE INVENTION

Therefore, what is needed is a communications system for use in a remotecontrol system which provides for increased data carrying capacity andexpandability. In particular, what is needed is a communications systemwhich uses a message protocol that provides for the ability toefficiently transmit and receive an increased amount of data, as well asdifferent types of data, compared to existing remote control messageprotocols. Further, what is required is a message protocol which can beexpanded to carry an additional amount of data and/or more types ofdata, yet remain both forward and backward compatible with existing andfuture receiver/decoders.

The present invention involves a communications system that uses amessage protocol which provides for the transmission and receipt ofcomplex data, as well as different types of data, such as ASCII data,and allows for expansion of the message as required, in an efficientformat. The present communications system and message protocol issuitable for transmitting and receiving remote control messages in RFsignal form, and especially suitable for transmitting and receiving a RFsignal in combination with an IR signal by time multiplexing the twosignals.

In accordance with one aspect of the present invention a remote controlapparatus is provided, comprising an input device for receiving remotecontrol messages from a user, a signal transmitter, and a controlleroperatively coupled to the input device and the signal transmitter, thecontroller generating a remote control message and causing the signaltransmitter to transmit the remote control message in response to theuser input, the remote control message comprising a plurality of datafields, each of the data field ending with an end of field marker, theplurality of data fields comprising a status field having signaltransmission information including a keycode type bit, and a keycodefield having one of first and second data in accordance with a state ofthe keycode type bit.

In accordance with another aspect of the present invention, a remotecontrol system is provided, comprising an input device for receivingremote control messages from a user, an IR signal transmitter, a RFsignal transmitter and a controller operatively coupled to the inputdevice, the IR signal transmitter and the RF signal transmitter, thecontroller generating an IR remote control message and a RF remotecontrol message and causing the IR signal transmitter and the RF remotesignal transmitter to transmit the IR and RF remote control messages,respectively, in a time multiplexed manner in response to the userinput, the RF remote control message comprising a plurality of datafields, each of the data fields ending with an end of field marker, theplurality of data fields comprising a status field having signaltransmission information including a keycode type bit, and a keycodefield having one of first and second data in accordance with a state ofthe keycode type bit.

In accordance with another aspect of the present invention, a remotecontrol apparatus is provided comprising an input device for receivingremote control messages from a user, a signal transmitter, and acontroller operatively coupled to the input device and the signaltransmitter, the controller generating a remote control message andcausing the signal transmitter to transmit the remote control message inresponse to the user input, the remote control message comprising astart sequence comprising a pulse and pause period having about equalduration, a preamble field having data for addressing a destinationdevice, a security code field having an identifier associated with saidsignal transmitter, a status field having signal transmission statusinformation, a keycode field having either a first or second data inaccordance with a keycode type bit in the status field, a checksum fieldfor verifying transmission integrity of the remote control message andan end of message marker.

In accordance with another aspect of the present invention, a remotecontrol apparatus is provided comprising a signal receiver adapted toreceive a remote control message, a controller operatively coupled withthe signal receiver, the controller adapted to decode and process theremote control message, the remote control message comprising aplurality of data fields, each of the data fields ending with an end offield marker, the plurality of data fields comprising a status fieldhaving signal transmission information including a keycode type bit, anda keycode field having one of first and second data in accordance with astate of the keycode type bit.

In accordance with another aspect of the present invention, a method oftransmitting a remote control message is provided comprising the stepsof: receiving a user input; generating a remote control messagecorresponding to the user input, the remote control message comprising astart sequence followed by a plurality of data fields and an end ofmessage marker, each of the data fields ending with an end of fieldmarker, the plurality of data fields comprising a preamble field havingdata for addressing a destination device, a security code field havingan identifier associated with the remote control apparatus, a statusfield having transmission status information about the remote controlmessage, a keycode field having data associated with the user input anda checksum field for verifying transmission integrity of the remotecontrol message; and applying the remote control message to a signaltransmission circuit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein:

FIG. 1 is a block diagram showing the elements of a remote controldevice suitable for use in the present communications system;

FIG. 2 is a block diagram illustrating the basic elements of a suitableRF signal transmitter;

FIG. 3 is a block diagram illustrating the basic elements of a suitableRF signal receiver;

FIG. 4 is an illustration of a transmission sequence of IR and RF remotecontrol messages wherein the IR and RF messages are transmitted in timemultiplexed manner;

FIG. 5 is an illustration of the data fields in a remote control messageprotocol of the present communications system;

FIG. 6 is an illustration of the waveform of the MARK and SPACE portionsof the remote control message protocol;

FIG. 7 is an illustration of a waveform of a symbol in the remotecontrol message protocol;

FIG. 8 is an illustration of a waveform of a remote control messageusing leading zero suppression;

FIG. 9 is an illustration of adding a new data field in the remotecontrol message protocol;

FIG. 10 is an illustration of expanding a pre-existing field in theremote control message protocol;

FIG. 11 is an illustration of using leading zero suppression whenexpanding a pre-existing field in the remote control message protocol;

FIG. 12 is a block diagram illustrating the basic elements of a signalreceiver/decoder suitable for use in the present communications system;and

FIG. 13 is a flowchart diagram illustrating the steps of a debouncingmethod.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

Referring to FIG. 1, there is shown a simplified block diagram of remotecontrol 10 suitable for use with the present communications system.Remote control 10 may take many forms, such as a stand alone unit or aportion of a larger communications device, and be adapted for use with avariety of electronic devices. For example, devices which incorporatethe elements and signal transmission features of remote control 10include, but are not limited to, a wireless keyboard, wireless pointingdevices and handheld remote control devices for controlling consumerelectronic devices. It is to be understood that the present remotecontrol may be used with any system adapted to transmit, receive orprocess remote control messages in response to a user input.

Generally, user input is received through input device 20 which includesvarious control buttons, device selection buttons, numerical buttons andthe like. It is to be understood that input device 20 may include anydevice whereby the user can provide an input to remote control 10 andincludes, but is not limited to, a keypad matrix, mouse, trackball,joystick and other types of pointing devices. Input device 20 isoperatively coupled to controller 14 which controls the overalloperation of remote control 10. Controller 14 receives the user input,and generates and causes the transmission of an appropriate remotecontrol message. Controller 14 may comprise any one of a plurality ofconventionally known devices, which may be in integrated circuit form,that are capable of performing control functions. Suitable controllersinclude, but are not limited to ST 7291 and ST 7225 manufactured by SGSThomson Microelectronics. The timing of controller 14 is controlled bycrystal oscillator 18.

Upon receiving a user input from input device 20, controller 14 uses thedesignated reference code, or other identifying information to look upthe desired information from the product code look up tables stored inmemory 22 in order to identify and generate a remote control messagehaving the correct signal structure. The signal structurecharacteristics include, but are not limited to, the proper carrierfrequency, pulse width, pulse modulation and overall signal timinginformation. Memory 22 may comprise RAM and/or ROM and be located eitherinternal or external to an enclosure associated with remote control 10.Controller 14 applies the appropriate remote control signal to IRtransmitter 16 and/or RF transmitter 17 to send the signal to thedestination device. Controller 14 also controls display 12, which mayinclude, for example, indicator LEDs, to indicate that a remote controlmessage has been transmitted. When the remote control message istransmitted, an IR receiver and/or a RF receiver associated with thedestination device detects the remote control message and provides themessage to the processor of the destination device for decoding andprocessing.

FIGS. 2 and 3 show RF transmitter 40 and RF receiver 50, respectively,suitable for use in sending and receiving RF messages in the presentcommunications system. As shown in FIG. 2, RF transmitter 40 comprisesbipolar oscillator 46 with a one-port SAW resonator for frequencystabilization coupled to mixer 44, which drives a linearly polarizedloop antenna 48 which is typically located in the enclosure of remotecontrol 10. When the user provides an input, for example by pressing akey, controller 14 generates a modulating signal which is used to turnoscillator 46 ON and OFF for amplitude shift keying of the carrier. Itis generally desirable that transmitter 40 include minimal parts due tolimited space in the enclosure of remote control 10.

A suitable RF receiver 50 is shown in FIG. 3. RF receiver 50 willtypically be located in, or connected to, the enclosure of thedestination device. The receiver is capcitively coupled to antenna 52,which may advantageously be a line cord that acts as a receive antenna,in which case the RF signal enters through a connector disposed on theenclosure around RE receiver 50. The signal is amplified by low-noiseamplifier 54, which decreases the total system noise level whileincreasing receiver sensitivity. The output of amplifier 54 passesthrough image filter 56 which provides rejection to the image frequency.The signal is then converted via mixer 58 and local oscillator 60 to anintermediate frequency (IF) of 10.7 MHz. The IF signal is passed throughfilter 62 and amplified by a chain of high gain logarithmic amplifiers64 which convert the signal into an output current. The output currentis converted to a voltage, passed to a noise adaptive thresholdcomparator 66, and lowpass filtered by data filter 68 before being sentto the processor of the destination device for decoding and processing.

Any one of a number of conventionally known IR transmitter and IRreceiver arrangements may be used to send and receive IR remote controlmessages in the present invention. Generally, an IR transmitter includesan LED coupled to an LED driver circuit which is controlled bycontroller 14. In response to a user input, controller 14 generates anIR remote control signal in accordance with the look up table in memory22 and applies the IR remote control signal to the LED driver circuit.The LED driver circuit drives the LED to project an IR signal toward thecontrolled device. An IR light sensor in the IR receiver detects the IRsignal and provides the signal to a processor in the destination devicefor decoding and processing. Suitable IR and RF transmitter and receiverarrangements include, but are not limited to, those found in DSS SystemDS5450RB manufactured by Thomson Consumer Electronics Inc., ofIndianapolis, Ind.

Remote control 10 transmits the IR signal, the RF signal or anycombination thereof for controlling an electronic device in response touser input. Advantageously, in order to transmit both an RF signal andan IR signal for each user input, wherein each signal is generatedaccording to a respective message protocol, remote control 10 maytransmit the two messages in a time multiplexed manner. In particular,the IR and RF signals may be transmitted in alternating fashion with theRF signal transmitted during the pause interval of the IR signal asshown in FIG. 4. In signal transmission sequence 70, the IR signals aretransmitted during intervals 74 and 78 while the RF signals aretransmitted during pause intervals 72 and 76.

The transmission sequence described above is particularly suitable foruse with existing IR signal protocols as such protocols usually requirerepeated intervals of IR signal transmission interrupted by pauseintervals. RF signals can easily be transmitted during the pauseintervals without affecting the IR signal transmissions. Typically, thepause interval between the IR transmissions lasts between 2-10 mS. Sucha sequence may be implemented using relatively inexpensive controllers.An apparatus and a method for transmitting IR and RF messages in such amanner is described in co-pending U.S. patent application Ser. No.09/331,996, entitled “Remote Control Apparatus and Method” which isassigned to the assignee of the present application.

The present communications system uses a remote control message protocolwhich is particularly suitable for transmitting RF remote controlmessages in the above-described multiplexed manner. The data fieldstructure and associated timing of the present remote control messageprotocol allow a RF message using the present remote control messageprotocol to be easily transmitted in the pause intervals as describedabove. However, it is to be understood that the present remote controlmessage protocol may be used with any signal transmission media, such asIR transmissions, and may be used for any message transmission method,and is not limited to use in multiplexed transmission schemes.

The structure of the present remote control message protocol is shown inFIG. 5. The remote control message 80 comprises a start sequencecomprising MARK/SPACE combination 82 followed by a plurality of datafields. The illustrated remote control message comprises five datafields. However, as described further below, the number of data fieldsmay be increased if the remote control message needs to be expanded inorder to encompass increased functionality. Each field ends with End ofField (EOF) marker 85. Use of an EOF marker allows the size of aparticular field to expand without changing the existing data fields inthe message protocol. The end of the message is marked by End of Message(EOM) marker 87. Use of an EOM marker allows the number of fieldstransmitted in the remote control message to be increased withoutchanging the existing data fields in the protocol. It can be seen thatuse of EOF marker 85 and EOM marker 87 allows the present messageprotocol to handle an increasing number of devices and functions withoutaltering existing RF systems in the field.

The format of MARK/SPACE combination 82 and the data within the datafields are now described. The MARK/SPACE combination 82, as shown inFIG. 6, signals the beginning of a new remote control message and isused by the destination receiver to distinguish the start of the messagefrom pulses caused by background noise. MARK pulse 102 is designed to bewider than the sync pulses that make up the rest of the remote controlmessage. The special length of MARK pulse 102 and the following pauseperiod, namely SPACE 104, allows the receiver/decoder to recognize thebeginning of the remote control message from background noise andpartial messages from other remote control devices. Suitable timing forMARK pulse 102 and SPACE 104 are shown in table 1 below (units in uS):

TABLE 1 Minimum Typical Maximum MARK pulse width 90 100 110 SPACE signaltime 90 100 110

Following the MARK and SPACE, the signal transmitter transmits aplurality of data fields. The data in each data field comprise aplurality of symbols including: “1”, “0”, and EOF. The remote controlmessage ends with the EOM symbol. Each of the symbols comprises awaveform comprising a sync pulse and a pause space, and as shown in FIG.7, waveform 105 is defined by sync pulse width 106 and total symbol time108. Suitable values for the sync pulse width 106 and total symbol time108 for each symbol are shown in table 2 below (units in uS, except EOMwhich is in mS):

TABLE 2 Minimum Typical Maximum Sync pulse width (all symbols) 45  50 55 “1” total symbol time 160 175 190 “0” total symbol time 210 225 240EOF total symbol time 260 275 290 EOM total symbol time .30  65 infinite

Each data field contains 8 bits of data and is transmitted in the orderof least significant bit first to the most significant bit last. Thedata fields also feature leading zero suppression to reduce datatransmission time, whereby any of the most significant bits nottransmitted for a particular byte when the EOF signal is received areassumed to be “0”. The structure and transmission order, from left toright, of a sample data field is shown below:

BIT0 BIT1 BIT2 BIT3 BIT4 BIT5 BIT6 BIT7 EOF

If the field has at least one most significant bit that is zero (databyte less than 80 hex, bit 7 or more clear), then these bit(s) would notbe transmitted and an EOF marker is transmitted after the final set bit.An EOM marker would replace the EOF marker for the last field, signalingthe receiver that no more fields are forthcoming and processing of themessage may begin.

An example of a remote control message that demonstrates the use ofleading zero suppression, as well as illustrates the use of the varioussymbols described above, is shown in FIG. 8. In FIG. 8, remote controlmessage 110 comprises start sequence 112, followed by data fields113-116 and EOM marker 117. Data fields 113-116 transmit “0D”, “00”,“0E” and “3B” respectively. Byte “00” is represented with only an EOFsymbol, with all leading zero bits suppressed. Also, EOM marker 117replaces the EOF marker for the last field 116.

The data associated with each of the data fields shown in FIG. 5 is nowdescribed. The preamble field comprises an identifying code associatedwith the destination device and is used to address the destinationdevice. The code data in the preamble field may correspond to thepreamble codes used in a pre-existing remote control message protocol,for example Thomson Consumer Electronics, Inc. Specification 15206770.All preamble fields for valid RF devices should correspond with theassigned preambles per the manufacturer's specifications.Advantageously, the preamble of future RF compatible products may bedesigned to be addressable using existing IR preamble codes.

The privacy code field comprises a 3 digit number in the range from000-255 which is programmed into remote control device 10 by the userand uniquely identifies the source of the remote control messagetransmission. The privacy code allows the receiver to respond only tothe proper remote control device and messages carrying incorrect privacycodes are ignored. The receiver for the destination device includes itsown use interface for determining what privacy code to accept Theprivacy code feature is particularly advantageous in RF signaltransmission applications for preventing neighboring RF transmittersfrom affecting the destination device and the present remote controldevice from affecting neighboring RF receivers. As such, the privacycode feature is particularly beneficial in densely populated areaswherein many other RF remote control devices may be operating. Thepreamble and security code fields are transmitted first to allow earlyrejection of the message by the destination device to improve theperformance of the system.

The privacy code feature also provides for additional addressingcapability if several receivers within range use the same preamble code.For example, if a user wishes to control 4 Digital Satellite System(“DSS”) receivers wherein the DSS remote control which includes keys for“DSS 1” and “DSS 2”, a pair of DSS receivers may be associated with “DSS1” key and configured to respond to a first and second privacy codes,respectively, and another pair of DSS receivers may be associated with“DSS 2” key and configured to respond to the first and second privacycodes, respectively.

Any conventionally known method for programming remote control devicesmay be used to assign the security codes, for example, the user mayprogram the remote control device by pressing an appropriate device key,for example, TV, VCR or DSS, and then entering a security code, forexample a three digit code. Alternatively, the user may be guidedthrough the programming sequence by an appropriate user interface, forexample, a menu on an On Screen Display.

The status field provides status information about the remote controlmessage transmission and includes the following flags:

Bit 7-Bit 2: currently unused

Bit 1: Keycode type

Bit 0: Keypress status

The keycode type bit (bit 1) indicates that the data carried in thekeycode field is one of two types of data depending on the status of bit1, for example a standard Thomson Consumer Electronic (“TCE”) keycodedata or ASCII character data byte from an alternative device, such as akeyboard, mouse, trackball, etc.

The keypress status bit (bit 0) toggles with each new key press onremote control device 10. The keycode type bit, along with timing of themessage separation assists the receiver in determining whether a messageis a repeated message from a single keystroke or the result of anotherkey press on remote control device 10. As described further below thekeycode type bit is used in a debouncing method to distinguish newkeypresses of remote control 10 from old ones thereby preventing thereceiver from performing multiple responses to a single keypress onremote control device 10.

Bit 7 through bit 2 are reserved for future expansion and should defaultto a “0” to take advantage of the leading zero suppression feature ofthe present remote control message protocol.

The keycode data field includes the data associated with the user input,such as a command or character data associated with a particular key.The data carried in this field may comprise data of any suitable formatfor transmitting the user input. In the present remote control messageprotocol, the data carried in this field comprises either a standard8-bit keycode associated with a pre-existing IR protocol, such as theThomson Consumer Electronics, Inc. Specification 15206770, or an ASCIIcharacter data byte depending on the status of the keycode type bit inthe status field.

The checksum byte field is used to verify accurate receipt of the remotecontrol message for all fields in the remote control message up to, butnot including the checksum field. All fields preceding the checksumfield are summed using 8-bit addition and the result is transmitted inthe checksum field.

The present remote control message protocol may be modified to addadditional data to the message while maintaining forward and backwardcompatibility with future remote control transmitters and receivers.Modification of the present remote control message protocol may benecessary, for example, to accommodate additional electronic devices oradditional functions for a particular electronic device. Themodification to the present remote control message protocol may takemany forms, including, but not limited to, adding a new field of data,expanding a field beyond 8 bits, and adding additional status bits.

Modification of the present remote control message protocol to add a newdata field is illustrated in FIG. 9. A new data field may be requireddue to, for example, the addition of a new feature in remote controldevice 10 or in the destination device. The new field 152 is insertedbetween the existing data fields 151 and checksum field 153, which isalways the last field of the message. The additional data fieldincreases the overall length of the remote control message, but does notaffect existing data fields 151 of the remote control message. In thismanner, the present remote control message protocol may be easilymodified to add additional features and still be able to controldestination devices that are based on older versions of the protocol.

Modification of the present remote control message protocol to expand afield size is illustrated in FIG. 10. Expansion of a field may benecessary to accommodate, inter alia, additional types of remote controldevices and increased functionality of existing remote control devices.If a field requires an increase in size beyond 8 bits, a new field isadded and placed immediately before the original field that requiredexpansion. In the example shown in FIG. 10, expansion of the keycodefield is realized by adding a keycode high byte field 163 between statusfield 161, and keycode field 162 and checksum field 164. If theexpansion of the keycode requires an increase from 8 to 10 bits, thenthe bits would be transmitted in the order shown in FIG. 11. In such acase, bits 9 and 10 of the keycode high byte would be located in bit 0and 1 of the high byte field 171, respectively, while the remaining bitsare transmitted in field 172. Field 172 should always be transmitted,even if the additional bits are all “0” and only the EOF symbol istransmitted. This allows the decoder in the destination device todistinguish what version of the protocol is being transmitted.

With regard to adding additional status information, the additionalstatus bits are allocated starting from the first available unused leastsignificant bit to reduce transmission time. If all 8 bits of the statusfield become allocated, an additional field is added, as describedabove, immediately prior to the existing status field.

A receiver/decoder may be programmed to determine the version of thereceived remote control message by examining the number of fields and/orthe number of bits in a particular field of data. By determining theremote control message version in this manner, current receiver/decoderscan maintain forward compatibility, i.e., process future version of thepresent remote control message protocol, and future receiver/decoderscan maintain backward compatibility, i.e., process past versions of thepresent remote control message protocol.

Forward compatibility is maintained by designing the receiver/decoder toprocess additional fields from future versions of the protocol only forthe purpose of calculating the checksum and assume the last field to bethe checksum byte. For example, since the original version of thepresent remote control message protocol contains 5 fields,receiver/decoders designed to process only this version of the remotecontrol message protocol would use only the first four fields anddisregard the remaining fields, but would sum all of the field in thereceived remote control message, including those after the first four,for the checksum and compare the result to the checksum field. Futuretransmitters utilizing the present remote control protocol should bedesigned to send the checksum field last so earlier versionreceiver/decoders will correctly process the basic message.

Backward compatibility is maintained by designing the receiver/decoderto always check for earlier versions of the remote control messageprotocol by examining the number of data fields received and process theremote control message accordingly. If a status bit is added to theoriginal status field, then the polarity of the new flag should beoriented such that an older version remote, i.e., one that does nottransmit the bit and thus defaults it to “0”, does not cause anyunwanted action in the receiver.

As indicated above, the present remote control message protocol isparticularly suited for transmission in RF signal form, especiallyduring the pause intervals of IR remote control signal transmissionintervals. The waveforms defined above and their associated timingensure that the RF messages can be transmitted during such periodswithout adversely affecting the IR transmission. The present messageprotocol also allows additional types of data to be transmitted andallows for expansion to accommodate increased functionality, as well aspermit forward and backward compatibility. Further, the present messageprotocol provides for security codes for preventing unwantedinterference from other RF remote controls.

A suitable receiver for detecting, decoding and processing the IR and RFsignals discussed above is now described. As shown in FIG. 12, suitablereceiver 200 comprises controller 202 which receives the IR and RFsignals through IR signal receiver 208 and RF signal receiver 210.Controller 202 decodes and processes the received remote control signaland sends control signals to device mechanism 206 to perform theoperation specified by the received remote control signal. Devicemechanism 206 comprises any one of a plurality of components included inan electronic device that may be controlled by the remote controlsignal. Such components include, but are not limited to, RF tuners, VCRtape transport, DSS transport decoder and TV tube deflection hardware.Controller 202 is also connected to memory 214 and display 204, whichmay include, for example a front panel indicator for displaying thestatus of the receiver, a set of indicator lights, an alpha-numericdisplay or a display screen. The timing of controller 202 is controlledby oscillator 212.

When an IR signal is directed at receiver 200, IR signal receiver 208detects and provides the IR signal to controller 202. Controller 202decodes and processes the received IR signal based on the appropriate IRformat specification. Likewise, controller 202 receives RF signals viaRF signal receiver 210 and decodes and processes the received RF signalbased on the appropriate RF format specification. The elements ofreceiver 200 and their operation are generally known in the art.

Receiver 200 may be designed to perform the receiving, decoding andprocessing functions in a number of predetermined modes or modesselected by a user. First, controller 202 may be programmed to decodeand process the IR and RF signals in the order that the signals arereceived. In such a case, controller 202 sends the necessary controlsignals to receiver mechanism 206 as the respective remote controlsignals are detected.

Second, receiver 200 may be arranged to decode and process the incomingsignals according to a predetermined priority or a priority selected bya user. For example, if IR signals are selected as higher priority,controller 202 may be programmed to ignore RF signals, or to store theRF signals for processing at a later time if IR signals are present.Also, higher priority may be given to a particular signal in the form ofinterrupting the decoding process to service the higher priority signal.For example, if IR signals are selected as higher priority, controller202 may be programmed to temporarily stop processing RF signals anytimean IR signal is detected. The priority selections may be made using anyconventionally known method, including, but not limited to using an OnScreen Display menu.

Receiver 200 may also be arranged to respond to only one type of signal,or set of signals, and ignore other type of signals. For example, ifreceiver 200 is programmed for use with only IR signals, controller 202would ignore all RF signals. Again, receiver 200 may be selected torespond to or ignore particular signals using conventional userinterface methods. Although FIG. 12 shows IR signal receiver 208 and RFsignal receiver 210, it is to be understood that the receiverarrangements described above may be implemented in a receiver having aplurality of signal receiver types and any number of signal receivers.

Due to the repeated RF signal transmission intervals associated witheach user input and the possibility of interference corruptingindividual messages when the present remote control message protocol istransmitted in RF form, a RF receiver/decoder associated with thedestination device should contain processing to determine if a receivedmessage should be acted upon or ignored. A suitable processing method isdescribed below. Such a method may be implemented on the RFreceiver/decoder by programming a destination device controller as knownin the art. The present method allows the RF receiver/decoder todistinguish new keypresses of remote control 10 from old ones. This isnecessary to prevent the RF receiver/decoder from performing multipleresponses to single keypresses of the remote. The two basic inputs tothe present method are the timing from the last operation and the stateof a keypress status bit in the status field of the message protocoldescribed above.

The timing from the last operation is measured by two separate timers, ashort timer and a long timer. The timers may be implemented in softwareor in hardware, e.g., as part of the controller IC. The short timerdetermines if the repeated messages from a single remote keypress havecome to an end or if a message is missing from the middle of a repeatedsequence. The long timer is used to determine if a keypress status bitshould be checked. The keypress status bit is a status flag that istoggled with each keypress. Suitable timer values for the short timerare 4-6 mS and for the long timer are 900-1100 mS.

The short timer is setup for a time that would not expire when arepeated RF message is received, yet will expire if a message is missingfrom the repeated sequence due to interference or a key release. Thelong timer is setup for the period that the requested function should berepeated if a remote key is held down indefinitely. The timers are resetafter the RF receiver performs the requested operation from the remoteand run until the receiver processes a new valid RF command.

A flowchart for implementing the present method is shown in FIG. 13.After performing the operation from the previous RF message in step 182,the RF receiver controller resets the long and short timers in step 184and waits for a new RF message. When a new RF message is detected instep 186, the receiver controller determines whether the long timer hasexpired in step 188. If so, the receiver controller performs theoperation of the new RF message. If not, the receiver controller checkswhether the short timer has expired in step 190. If not, the receivercontroller returns to step 186 to detect a new valid RF message. If so,the receiver controller checks whether the keypress status bit hastoggled in step 192. If so, the receiver controller performs theoperation of the new RF message. If not, the receiver controller returnsto step 186 to detect a new valid RF message. Therefore, it can be seenthat the operation for a new RF message is performed if the long timerhas expired or if the short timer has expired and the keypress statusbit in the RF message has toggled to indicate a new keypress.

The present remote control message protocol is suitable for use inautomatically detecting the message format wherein a detector isprogrammed to automatically determine the format, or version, of themessage protocol based on the data transmission speed. Such an automaticformat sensing method advantageously utilizes the leading zerosuppression feature of the present remote control message protocol. Inthe leading zero suppression technique, the first bit transmitted isalways a logic one, therefore, a signal receiver may be adapted todetermine the speed of data transmission by measuring the width of thefirst symbol. Knowing that various data transmission speeds correspondto various formats, the receiver and associated processor may be adaptedto automatically sense which format is being received and adjust thedecoding accordingly. In the embodiment described above, controller 202would be programmed to automatically determine the incoming messageformat by measuring symbol width 108 of the first symbol after startsequence 82 in message 80.

The determination of data transmission speed need not be limited to adetermination based on a width measurement of the first symbol. Thestructure of the present remote control message protocol is based onsymbol encoding of a basic time interval. Therefore, any part of, or theentire message may be used to determine the data transmission speed andformat, for example, the EOF marker. Specifically, if memory isavailable to store the entire message without decoding in on the fly,many powerful signal processing techniques can be used.

Adjusting the data transmission speed may be useful for allowing fasterformats for the future that are compatible with the existing formats.However, it is to be understood that the present automatic formatsensing method is not limited to faster formats. A slower speedimplementation could also be used, for example, if the implementationprovided a cost advantage.

The speed values may be limited to discrete values or allowed to varyover a continuous scale. In this regard, limiting the speed values todiscrete values may be more advantageous than allowing a continuouslyvarying scale for the pulse widths due to environmental noise factorsand pulse distortions in the receiver.

It will be apparent to those skilled in the art that although theinvention has been described in terms of an exemplary embodiment,modifications and changes may be made to the disclosed embodimentwithout departing from the essence of the invention. For example, remotecontrol 10 may be of the universal remote control type which is capableof controlling one of a plurality of designated electronic devicesaccording to a reference code, or other signal format identifyinginformation, selected by the user. The reference code may be selectedusing for example, the direct, manual entry method, the semi-automaticstepping entry method, the automatic entry method, or any other suitablemethod of selecting and entering a reference code. In that case, remotecontrol 10 uses the identifying information to generate the appropriatesignal associated with the particular manufacturer and model.

Therefore, it is to be understood that the present invention is intendedto cover all modifications as would fall within the true scope andspirit of the present invention.

What is claimed is:
 1. A remote control apparatus, comprising: an inputdevice for receiving remote control messages from a user; a signaltransmitter; and a controller operatively coupled to said input deviceand said signal transmitter, said controller generating a remote controlmessage and causing said signal transmitter to transmit said remotecontrol message in response to the user input, said remote controlmessage comprising start sequence followed by a plurality of datafields, each said data field ending with an end of field marker, saidplurality of data fields including a status field having a message typeidentifier which identifies a particular message protocol, and a keycodedata field carrying keycode data, said keycode data formatted inaccordance with said particular message protocol.
 2. The remote controlapparatus of claim 1, wherein said keycode data comprises one of astandard remote control protocol formatted data and ASCII characterdata.
 3. The remote control apparatus of claim 1, wherein said startsequence comprises a pulse and a pause period having substantially equalduration.
 4. The remote control apparatus of claim 1, wherein saidremote control message further comprises an expansion data field and anend of message marker, said controller transmitting said remote controlmessage in the order of, said start sequence, said plurality of datafields, said expansion data field, and said end of message marker. 5.The remote control apparatus of claim 1, wherein said remote controlmessage further comprises a field expansion data field associated withone of said plurality of data fields and an end of message marker, saidcontroller transmitting said field expansion data field immediatelyprior to said associated data field.
 6. The remote control apparatus ofclaim 1, wherein said signal transmitter is a RF signal transmitter. 7.The remote control apparatus of claim 6, wherein said plurality of datafields further comprises a preamble field having data for addressing adestination device, a security code field having an identifierassociated with said signal transmitter, and a checksum field forverifying transmission integrity of said remote control message.
 8. Theremote control apparatus of claim 7, wherein said security code datacomprises a three digit code programmed into said controller by theuser.
 9. The remote control apparatus of claim 7, wherein saidcontroller generates said remote control message using leading zerosuppression.
 10. The remote control apparatus of claim 9, wherein saidsecurity code data is programmed into said controller using an On ScreenDisplay menu.
 11. A remote control system, comprising: an input devicefor receiving remote control messages from a user; an IR signaltransmitter; a RF signal transmitter; and a controller operativelycoupled to said input device, said IR signal transmitter and said RFsignal transmitter, said controller generating an IR remote controlmessage having pause intervals and a RF remote control message, said RFremote control message comprising a start sequence having a pulse and apause period having substantially equal duration followed by a pluralityof data fields, each said data field ending with an end of field marker,said plurality of data fields including a status field having a messagetype identifier which identifies a particular message protocol, and akeycode data field carrying keycode data, said keycode data formatted inaccordance with said particular message protocol, said controllercausing said IR signal transmitter and said RF signal transmitter totransmit said IR and RF remote control messages, wherein said RF remotecontrol message is transmitted during the pause intervals of said IRremote control message.
 12. The remote control apparatus of claim 11,wherein said keycode data comprises one of a standard remote controlprotocol formatted data and ASCII character data.
 13. The remote controlapparatus of claim 11, wherein said RF remote control message istransmitted in the order of, said start sequence, a preamble fieldhaving data for addressing a destination device, a security code fieldhaving an identifier associated with said signal transmitter, saidstatus field, said keycode field, a checksum field for verifyingtransmission integrity of said RF remote control message and an end ofmessage marker.
 14. The remote control apparatus of claim 13, whereinsaid controller generates said RF remote control message using leadingzero suppression.
 15. The remote control apparatus of claim 13, whereinsaid security code data comprises a three digit code programmed intosaid controller by the user.
 16. The remote control apparatus of claim15, wherein said security code data is programmed into said controllerusing an On Screen Display menu.
 17. A method of transmitting a remotecontrol message, comprising the steps of: receiving a user input throughan input device; generating an IR remote control message associated withthe user input, the IR remote control message having pause intervals;generating a RF remote control message corresponding to the user input,the RF remote control message comprising a start sequence having a pulseand a pause period having substantially equal duration followed by aplurality of data fields and an end of message marker, each said datafield ending with an end of field marker, said plurality of data fieldscomprising a status field having a message type identifier whichidentifies a particular message protocol, and a keycode data fieldhaving keycode data formatted in accordance with the particular messageprotocol; and transmitting the IR and RF remote control messages bytransmitting the RF remote control message during the pause intervals ofthe IR remote control message.